IHU VARIANT OF COVID-19
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- IHU variant of Covid-19 has been detected in several countries.
- This variant, B.1.640, has been reported to have 46 mutations, including some in the spike protein.
- It is not as alarming as the spread of Omicron.
What is Mutation?
- A mutation is a change in a genetic code.
- Mutations can result from DNA/RNA copying mistakes made during replication of repeating elements.
Basics of DNA and RNA
● DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms.
● The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
● DNA bases pair up with each other, A with T and C with G, to form units called base pairs.
● Each base is also attached to a sugar molecule and a phosphate molecule.
● Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix.
● An important property of DNA is that it can replicate, or make copies of itself.
● Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases.
● This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.
● Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes.
● Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA, RNA is found in nature as a single strand folded onto itself, rather than a paired double strand.
● Cellular organisms use messenger RNA (mRNA) to convey genetic information (using the nitrogenous bases of guanine, uracil, adenine, and cytosine, denoted by the letters G, U, A, and C) that directs synthesis of specific proteins.
● Many viruses encode their genetic information using an RNA genome example: SARS Cov-2.
SARS Cov-2 Mutants
- Viruses are continually evolving, and there is no exception for SARS-CoV-2.
- These genetic variants take place over time and can bring about new variants that may have distinct features.
- A study by CSIR-CCMB has found that in India alone, there are over 5,000 mutants of the virus causing Covid-19.
- Each SARS-CoV-2 includes approximately 30,000 letters of RNA. This genetic data enables the virus to attack cells and hijack them to replicate.
- Small copying mistakes called mutations are made when an infected cell builds new corona-viruses.
- A set of coronaviruses that share the identical inherited set of distinct mutations is referred to as a variant.
- There are lineages or clades or subtypes.
- Earlier, there was the ancestral type — the Wuhan virus type, from which 10 lineages had evolved.
- A lineage is given a name if its frequency reaches 20% globally.
- Further, an evolved lineage is given a separate identity if it differs from the existing lineages by at least two DNA changes (mutations).
- Based on the revised time-stamped nomenclature, there are now five lineages: 19A, 19B, 20A, 20B and 20C.
- The first two digits reflect the year in which the lineage evolved.
Few notable variants of SARS-CoV-2
- 1.1.7 Lineage, B.1.351 Lineage, P1 Lineage
- D614G: It is a mutation that alters the spike protein of the SARS-CoV-2 virus.
- E484K: E484K is described to be an “escape mutation” because it helps the virus slip past the body’s immune defence mechanism. The recent Bengal Strain has been formed by E484K mutation.
Variant of Interest
- WHO places a SARS-CoV-2 variant in the VOI list if it is seen to have certain “genetic changes that are predicted or known to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape”
- To be added to the VOI list, a variant must also be “identified to cause significant community transmission or multiple Covid-19 clusters in multiple countries”, and suggest “an emerging risk to global public health”.
‘Variants of Concern’ (VOC).
- More dangerous mutants are categorised as ‘Variants of Concern’ (VOC).
- According to the WHO, a VOI can become a VOC if it is demonstrated to be associated with
- an increase in transmissibility or virulence,
- a “decrease in effectiveness of public health and social measures or available diagnostics, vaccines, and therapeutics”.
- Currently, four variants of the coronavirus are designated as variants of concern. They are:
- Alpha (lineage B.1.1.7, the so-called ‘UK variant’),
- Beta (lineage B.1.351, the so-called ‘South Africa variant’),
- Gamma (lineage P.1, the so-called ‘Brazil variant’),
- Delta (lineage B.1.617.2), the variant that was first reported in India in October 2020 and is now present in at least 170 countries. The highly transmissible Delta variant is now the dominant strain of the virus in India, and was responsible for the devastating second wave of Covid-19 in April-May this year.
To know more about Mutation and variants of SARS-CoV-2 in detail visit: https://www.iasgyan.in/blogs/bengal-strain-all-about-mutation